1. Field of the Invention
The invention relates to an integrated charge pump, in particular for use in integrated circuits with reduced current consumption.
2. Description of the Related Art
Integrated circuits usually require, in addition to the external supply voltage, further internal voltages which do not correspond to the external supply voltage and are either larger or smaller than the external supply voltage or are provided with a different sign. In order to convert the external supply voltage into the respective internal supply voltage, a suitable voltage supply source is provided, which, for voltage conversion purposes, usually requires an additional operating current, e.g., for the voltage regulation, which additional operating current becomes apparent in the current balance of the entire integrated circuit. This additional current is essentially constant irrespective of what supply current is drawn at the output of the voltage supply source. In low-power applications, in which the voltage supply sources are operated both in a normal operating mode and in a standby operating mode, different supply currents are drawn from the voltage supply source depending on the operating mode. The efficiency of the voltage supply source deteriorates as the supply current decreases since, as mentioned previously, the additional current required, e.g., for the voltage regulation remains constant. Therefore, it is important, particularly in low-power applications, to optimize the efficiency of such voltage supply sources.
In the case of charge pumps, the supply current for the supply sources is determined to a considerable extent by the switching of transistors for changing over between a first and a second cycle. Thus, by way of example, switching devices are provided in a charge pump in order to optimize the operation of the charge pump, e.g., a switching device which, depending on the operating state, connects the substrate (back gate) of a switching transistor to the respective lowest or respective highest potential.